The synthesis and processing of nuclear and cytoplasmic transfer RNA (tRNA), ribosomal RNA (rRNA) and messenger RNA (poly(A)RNA) will be studied in L1210 and Ehrlich ascites cells. The effect of the antimetabolites: 5-fluorouracil, 5-azacytidine, dihydro-5-azacytidine, sangivamycin, tubercidin, formycin A, 8-Azaadenosine and cordycepin (3'-deoxyadenosine) will be examined on the methylation of rRNA and tRNA, as well as their synthesis to establish the relevance of these processes to the cytotoxicity of these agents.